1. Field of the Invention
The present invention relates to agricultural combines, and, more specifically to grain extraction in such machines.
2. Description of the Related Art
Combines are used to harvest agricultural crops such as corn, soybeans, wheat and other grain crops. As the combine is driven through crop fields, the combine cuts the crop, separates the desired crop from the undesired waste, also known as material other than grain (MOG), stores the crop and discards the waste.
In a typical combine, a header is mounted to the front of the combine to gather the crop and feed the crop into the combine for processing. As the combine is driven through the field, the crop material is collected by the header and deposited into a feeder housing. The material is then transported upwardly and into the combine by a feed elevator located within the feeder housing. The crop material then passes through a threshing and separating system. In a rotary combine, the threshing and separating system usually includes a rotor, a threshing concave, a rotor cage and a separating grate. As crop material passes between the rotor, the threshing concave and the separating gate, the crop material is impacted and/or rubbed thereby causing the grain to separate from the stalk material. The stalk material that is separated from the grain is commonly referred to as MOG. Other types of combines are known that perform similar functions using different mechanisms.
After passing through the threshing and separating system, the grain and MOG are deposited onto a grain cleaning system. The grain cleaning system of the typical combine includes a plurality of adjustable cleaning sieves often referred to as a chaffer sieve and a shoe sieve and sometimes a pre-cleaning sieve. These sieves are typically reciprocated back and forth in opposite directions along an arcuate path. This motion has the tendency to separate the grain from the MOG. To further separate the grain from the MOG, a cleaning fan or blower is positioned so as to blow air up through the cleaning sieves. This flow of air tends to blow the MOG, which is typically lighter than grain, rearwardly and out the back of the combine. Grain which is heavier than MOG is allowed to drop through the openings in the sieve.
The clean grain that falls through the cleaning sieves is deposited on a collection panel positioned between the cleaning sieves. The collection panel is angled so as to promote the grain to flow, under the influence of gravity, onto a conveyor such as an auger trough positioned along the lower most edge of the collection panel. The auger trough is typically positioned near the forward end of the cleaning sieves and extends along the width of the sieves. The grain collected in the auger trough is then moved by an auger towards the side of the combine where it is raised by a grain elevator and deposited into a storage tank or grain tank. Other systems also exist that can utilize for example, a loop conveyor system which eliminates the need for a conventional cross auger.
With the progression in the technology of the agricultural field, combines are being called on to be ever more efficient in the extraction of grain and the processing capacity for a given size. As the quantity of grain and MOG delivered to the threshing and separating system increases per unit of time, there is the tendency to locally exceed the capacity of the unit. It has been proposed, in an attempt to make the processing more efficient, to move some of the separating functions into the feeder housing and even the header for the combine. While these approaches have had some limited success, they do so at the expense of added complexity, cost and weight to the agricultural combine.
What is needed in the art therefore is a more efficient extraction of grain within an agricultural combine.